The present state of the electrolysis art is not commercially attractive for large scale hydrogen production because the cost of the electrical input energy ranges between 75% to 85% of the fuel value of the released hydrogen and oxygen gases.
This electrical cost is prohibitively high, when the gases must, in turn, be burned as fuel for home heating, for heat engine application and for a wide variety of small industrial applications.
Various alternate hydrogen generation processes have been considered in the past, but none have shown sufficient future potential, compared to the basic water/electrolysis method.
The dissociation of industrial ammonia has been considered, but in addition to the currently high cost of ammonia, the problems of a high heating source make this process less hopeful for further development effort.
The adaptation of the active metal series (calcium, sodium, potassium, etc.) as a useful hydrogen generation means has been reviewed, but it was found that the necessary supporting equipment becomes too complex. In addition to a basic process tank, various material supply and holding tanks are required, along with the interconnection and control means.
Some of the other remaining possible hydrogen production processes would also involve extensive supporting equipment, raw materials, and considerable space/volume requirements, making them generally less desirable for further development for most applications.
The water electrolysis process is basically clean and simple for obtaining both pure hydrogen and oxygen, and moreover lends itself to various output improvement modifications, such as the applying of heat energy, internal and external pressure, sonic-vibration energy, light/radiant energy, chemical boosting, and the use of permeable electrodes in conjunction with pressure, and other possible variations and combinations of these means.
When the various forms of supplemental energy are considered, as applied to the electrolysis process, certain means stand-out as more economical and attractive than others. As a general rule, pressure and vibratory energy can be viewed as cheaper than heat and most forms of radiant energy, while chemical means are somewhat uncertain due to the initial and replenishment costs.
The use of permeable membranes or porous metallic elements for gas permeation through the electrodes of the cell entail some uncertain factors at this point in the development work, such as the probable progressive clogging of the permeable elements by the pressurized electrolyte, and the possible water/electrolyte leakage into the gas collection zones.
It is now believed that these negative factors can be controlled and offset by the periodic reverse-flushing of the porous electrode elements, in the first case, and by use of an effective hydrophobic coating material on the porous electrodes, in the latter instance.
Another obvious point in favor of the basic water electrolysis process, is that oxygen--(approx. 33%) is simultaneously produced along with the hydrogen gas--(67%), which can be used for combustion support of the ignited hydrogen gas in a modified I.C., or E. C. engine. For some applications this oxygen gas may not be used, and if not collected and stored in storage tanks, may be vented to the atmosphere.
The purpose of any electrolysis modification or combination method is to substitute some form of convenient low cost energy for a portion of the high-cost electrical input energy, for producing a given volume of hydrogen and oxygen.
The applying of pressure is not new in the electrolysis art, since the known and used Noeggerath Cell employs a cell configuration of progressively confined spaces, which results in a gradual pressure rise as the gases are generated. By careful, planned construction of the cells, the gradual pressure rise can continued until a final pressure of about 200 atmospheres is obtained.
While the Noeggerath Cells utilize progressively increasing internal pressure, this present disclosure employs the applying of external pressure, acting on permeable electrode elements for accelerated permeation passage of both gases, unlike previous pressure type electrolysis cells.
The permeable pressure passage of gases is not new to the fuel cell art, in which some types of units employ permeable elements to allow the active gases to pass through them to generate electricity. A fuel cell provides an inverse function compared to an electrolysis cell, whereby an oxidant along with other fuels are introduced into the cell to generate electrical power.
Separation of hydrogen by permeation is known in the gas separation art, but previous separation methods have required the use of palladium, or palladium-silver alloys as the permeable barriers, which is now economically unacceptable for any commercial application.
A fine coating of palladium-black has been successfully used as a means of reducing the tendancy toward the "poisoning" of the permeable elements with an oxide film, but this advancement does not overcome the basic cost objection to the use of palladium or palladium metal alloys and heavy coatings.
The limited use of palladium and palladium-black film foruse in this invention for hydrogen permeable elements poses a specific difficulty in preventing electrode pore clogging, which must be overcome by the combined use of a near-surface plastic hydrophobic coating material, and the periodic reverse-flushing of the porous electrode tubular walls.
Although nickel and monel were the prime choices, and are now in use as the porous electrode material, vanadium has a lattice structure which is compatible with the diffusion of atomic hydrogen through it.
In the preliminary stages of the cell development, silicone was naturally proposed as a suitable hydrophobic medium to be impregnated into the porous electrode walls, but it was found that the silicone was gradually displaced by the pressureized electrolyte, so that it was dropped from further use for the cells.
The necessity of a permanent hydrophobic barrier layer was evident, and Teflon was suggested and used as a permeable subcoating, although Teflon does not exhibit a particularly high permeability rate to gas passage.
Other permeable plastic materials are now being tried and lifetested such as polyethylene and polystyrene coatings, which show greater gas permeability rates.
Another theory, yet to be tested, is the "salient point concept" in which a great number of random high points are located on the porous tubular electrode outer surface, so that the gas molecules tend to gather at these points. The theory behind this concept is that the salient points will tend to break up clogging in the local area of the points, aided by the input vibratory motion.